Distributor for internal combustion engines



2 Sheets-Sheet 1 mVEA/m? Sept. 17, 1963 H. MGLLER DISTRIBUTOR FOR INTERNAL COMBUSTION ENGINES Filed May l6. 1961 H. MOLLER 3,104,291 DISTRIBUTOR FOR INTERNAL COMBUSTION ENGINES Sept. 17, 1963 2 Sheets-Sheet 2 Filed May 16. 1961 United States Patent M The present invention relates to distributors for internal combustion engines.

Such distributors conventionally include an interrupter assembly having electrical contacts which move into and out of engagement with each other. It is desirable to be able to regulate the operation of the interrupter assembly in accordance with the speed of operation of the engine, and for this purpose the interrupter assembly is actuated by a cam which is driven from the engine. For the sake of making the most economical use of the fuel it is also desirable to be able to adjust the timing of the operation of the contacts, and for this purpose an adjustment is made from the vacuum which prevails in the intake manifold of the engine. Conventionally the interrupter structure is carried by a support plate which is movably mounted in the housing of the distributor, and the con-' nection between the intake manifold of the engine and this support plate is such that the support plate is moved with respect to the housing of the distributor so as to shift the interrupter assembly which is carried by the support plate, and in this way the location of the interrupter assembly with respect to the actuating cam is regulated so as to retard or advance the spark and in this way make the most economical use of the fuel. This conventional construction has the defect, however, of requiring the support plate during its adjustable movement to overcome a considerable amount of friction, and therefore the required adjusting movements of the support plate are obtained only with the greatest difficulty. Moreover, the masses which must be moved to effect this adjustment are undesirably large.

It is accordingly a primary object of the present invention to provide a distributor of the above type which is capable of effecting the adjustment of the interrupter assembly with respect to the actuating cam in a manner which requires only :an extremely small amount of friction to be overcome so that the adjustment can be made very easily.

It is also an object of the present invention to provide a structure where the adjusting movements require only relatively small masses to be moved so that from this standpoint also the adjustment is very easy to carry out.

Still another object of the present invention is to provide a structure of the above type which enables the relationship between the contacts of the interrupter assemblyto be adjusted so as to compensate for wearing away of these contacts after a period of use, for example.

Still another object of the present invention is to provide' for a distributor of the above type a structure com posed of a relatively small number of rugged elements which are very reliable in operation.

With the above objects in view the invention includes, in a distributor for an internal combustion engine, a rotary cam which tunls about its axis and a stationary support plate which is located adjacent to the cam in a plane normal to the axis thereof. An elongated interrupter means is located next to the plate and extends across the cam, and this elongated interrupter means includes 'a stationary contact, a movable contact, and a cam follower portion which is located in the path of movement of the cam to be actuated thereby for moving the movable contact with respect to the stationary contact.

A pair of linkage means are respectively located on op- 3,104,291 Patented Sept. 17, 1963 posite sides of the cam and this pair of linkage means connects the interrupter means to the plate for movement in a plane parallel thereto along a path which moves the cam follower portion, at least within a given range of adjustment, along a circle whose center is in the turning axis of the cam, so that in this way the adjustment of the timing so as to advance or retard the spark is carried out without the necessity of overcoming a large amount of friction and while requiring only relatively small masses to be moved.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a fragmentary plan view showing the interior of a distributor according to the present invention where the structure of the present invention is located;

FIG. la is a view similar to that of FIG. 1 showing the cam follower turned clockwise through an angle of 10;

FIG. 1b is a view similar to that of FIG. 1 showing the cam follower turned counterclockwise through an angle of 10;

FIG. 2 is a fragmentary sectional view taken along line IIII of FIG. 1 in the direction of the arrows;

FIG. 3 is a fragmentary plan view of a part of a distributor having another embodiment of a linkage means different from that of FIGS. 1 and 2; and

FIG. 4 is a fragmentary sectional view taken along line IV-IV of FIG. 1 in the direction of the arrows.

Referring to the drawings and to FIGS. 1 and 4 in particular, the distributor of the invention includes a support means formed by the distributor housing 10 and the stationary support plate 11 located therein. The support plate 11 is fixedly carried by the housing 10. For this purpose a screw 12 passes through a suitable opening of the housing 10 into threaded engagement with an upstanding lug of the support plate 11, as is particularly apparent from FIG. 4. This upstanding lug is shown in FIG. 4 provided with a threaded opening which receives the screw 12. As is apparent from FIG. 1 the support plate 11 has at its periphery on opposite sides of the upstanding lug which cooperates with the screw 12 a pair of portions 11' which are pulled tightly against the inner surface of the housing 10 by the screw 12, and the housing 10 has directl beneath the plate 11 a pair of inwardly extending portions 10' which engage the underside of the support plate 11. In a conventional manner the distributor includes a rotary cam 21 which is turnable about its own axis, this cam being driven in a conventional manner from the engine itself so as to also rotate at a predetermined portion of the speed of rotation of the crank shaft of the engine, and it will be seen that the support plate 11 is located adjacent to the cam 21 in a plane which is normal to the axis of the cam 21. Of course, this cam 21 turns about its own axis.

An elongated interrupter means extends along the upper side of the support plate 11 next to the latter across the cam 21, and this interrupter means includes a carrier plate 13 which is located next to the plate 11. At its left portion, as viewed in FIG. 1, the carrier plate 13 of the elongated interrupter means is provided with an upstanding lug 13' which fixedly carries the stationary contact 14 of the interrupter means. The interrupter means includes a movable contact '16 which cooperates with the stationary contact 14, and this movable contact 16 is carried by the lever 15 of the interrupter means. The interrupter means also includes a cam follower portion 17 in the form of plate 11.

stationary contact 14 as permitted by the turning of a crest of the cam 21 beyond the cam follower portion 17. A pivot means in the form of a pivot pin 19 is fixed to the carrier plate 13 of the interrupter means, as by being riveted thereto, and this pivot means 19 pivotally supports the lever 15 for turning movement with respect to the carrier plate 13. The carrier plate 13 carries a second pivot means 20 in the form ofa pivot pm which isalso fixed to the plate 13 as by being riveted thereto, both the pin '19 and the pin 24 extending upwardly from the plate 13, as

is particularly apparent from FIGS. 2 and 4.

A connecting means of the invention connects the interrupter means 13-49 to the support plate 11 for movement in a plane parallel thereto along a path which moves the cam follower portion, at least within a given range of adjustment, along a circlewhose center is in the axis of the cam 21, and this connecting means includes the pivot pin 22-which is fixed, as by riveting for example, to the support plate 11 and extends upwardl therefrom and the pivot pin 23. An adjustable connecting means is provided for adjusting the location of the pivot pin 23ywith respect to the plate 11, and for this purpose the pivot pin 23 is in the form of a screw member havinga head 23 and an opposed threaded portion 23" (FIG. 2), this latter threaded portion 23" threadedly carrying the nut 24. The nut 24 has directed toward the head 23' of .the bolt 23 a rectangular portion which is located in an elongated notch 25 formedin the support plate 11, and as is particularly apparent from FIG. 1 this rectangular portion has a rela- V which will move the cam follower portion 17 along a moves in a well-known manner in response to changes in the vacuum in the interior of the intake manifold of the engine, so that in this way the arm 27' will be moved as indicated by the double-headed arrow at the'lo-wer part of FIG. 1, and this movement will take place within a given range which will result in actuation of the parallelogram linkage so as to move the cam follower portion at least within this given range of movement along a circle whose center is in the axis of the cam 21, and in this way the structure of the invention operates to advance or retard the spark.

As is apparent from 'FIG. 1, the distance between the connection at 20 of the link 26 to the carrier plate 13 and the connection at 23 of the link 26 to the plate 11 is equal to the distance between the connection at-19 of the link 27 to the carrier plate 13 and the connection at 22 of the link 27 to the plate 11. In other words, the distance between the pins 20 and 23 equals the distance between the pins 159 and 22. Thus, straight lines interconnecting the centers of the pins 19, 2d, 22 and 23 will form a parallelogram whose sides are equal in length and do not change in a length during the adjusting movement of the interrupter means. In this way, when the interruptermeans is moved in response to turning of the extension 27 of the linkage means 27 the cam follower portion 17 which is directly engaged by the cam '21 will move along a circle whose center is in the turning axis of the cam 21; Of course, it

tively small play in the notch 25 so. that when the bolt 23 i is loosened the nut 24 can shift together with the bolt 23 along the notch 25 while turning of the bolt 23 will cause the nut 2 to become tightened thereon since the nut cannot turn because of its rectangular portion which is in the notch 25. At the underside of the plate 11 the nut 24 has a flange which extends beyond the notch 25 and engages the underside of the plate. 11 so that in this way the bolt 23 maybe tightly fixed in a selected position along the notch 25. ,As is apparent from FIG. 2, the bolt 23 includes at the junction bet-ween the threaded portion 23" t and the shank of the bolt a shoulder directed toward the nut 24 and receiving a washer which is capable of sliding along the upper face of the plate 11, this washer of course having a diameter greater than the width of the notch 25..

The connecting means includes on one side of the'cam 21,

in the embodiment of FIGS. 1 and 2, a linkage means formed by an elongated link 26 which extends generally in the direction of the notch 25 and which is formed at one end with an opening through which the pin 23 passes and at its opposite end with anjopening which the pivot pin 21} which is fixed to the carrier plate passes, so that in this way the carrier plate 13 is connected through the link 26 i V to the plate 11, and through the cooperation of the bolt 23 is formed at one end with an opening through which the pivot means 19 passes so that the pivotal connection of the linkage means 217 to the pin 19 and the pin 22 serves to pivotally connect the carrier plate '13 to the support Thus, the pair of linkage means 26 and 27 form by their connection with the interrupter means 13 is possible also to provide structures in accordance with the present invention where the links 26 and 27 are of different lengths and where the cam follower portion 17 will still turn, within the range of adjusting movement provided by the lever 27', along 'a circle whose center is in the axis of the cam 21.

The distance between the contacts 14 and 16 will not change during adjustment of the position of the interrupter means by turning of the lever 27'. However, it is possible to adjust the distance between the contacts'14 and 16 so as to compensate for wearing away of the contacts as the result of pitting, and the like. For this purpose the plate 11 fixedly carries a pair of projections 28 which extend upwardly from the plate 11, and the space between the projections 28 is aligned with a vertically extending notch 26 formed in the left face of the link 26, as viewed in FIG.

portion 17 so that the spring 18 will maintain the cam follower portion 17 in engagement with the cam .21 and thus the movable contact 16 will remain substantially stationary while during the longitudinal shifting of the link 26 the stationary contact 1 can have its distance with respect to the movable contact adjusted, and after the desired adjustment is made with the open contacts the bolt 23 is tightened so as to maintain this adjustment. j

I In the illustrated example the arm 27"between the pivotal connection 22 to the plate 11 and the pivotal connection to the link which extends to the diaphragm is approximately 2.5 times the length of the link .27, which is to say 19 andcthe support plate '11 a 'connectionmeans connecting the interrupter means to the support plate for rnovernent in a plane parallel to the support plate along a path the distance between the pins 19 and 22, and with this ratio between the arms 27 and 27' of the two-armed lever the various parts have with respect to each other such a relationship that when the lever 27 is turned for example through 5 the cam follower portion 17 will also turn through an angle of 5 around the axis of the cam; 21.

The cam follower portion 17 has a convex face which is directly engaged by the cam 21, and this convex face forms part of a cylinder whose axisis indicated at M, this cylinder axis extending parallel to the axis of the cam 21, and in the illustrated example the distance between the axis M and the axis of the cam 21 is equal to the distance between the pins 19 and 22, and the distance between the pins2ll and 23'. Thus, due to the above-described parallelogram linkage when the lever 27, 27 turns, the point M necessarily turns along a circle (partially shown by the dash-dot line in FIGS. lo and 111) whose center is in the axis of the cam 21. The condenser of the distributor is shown at the lower left portion of FIG. 1, and of course the electrical connections are purely conventional and are therefore not illustrated.

In the embodiment of FIG. 3 the linkage means on the leftside of the cam 21, as viewed in FIGS. :1 and 3, takes the'form of a leaf spring 34) instead of an elongated link 26. The leaf spring 30 is connected at one end to an upwardly directed lug 31 of the carrier plate 31 of the interrupter means of FIG. 3, this carrier plate 31 corresponding'to the carrier plate 13 described above. The other end of the leaf spring 30 is connected to an arm of an angle member 33, and a rivet 38 may be used to fix the leaf spring 30 to the angle member 33 while a similar rivet may be used to fix the leaf spring 30 to the lug 31' of the carrier plate 31 of the interrupter means of FIG. 3. The angle member 33 is adjustable with respect to the support plate 32 which corresponds to the support plate 11 described above. 7 At its lower Wall which is located directly next to the support plate 3-2, the angle member 33 is formed with an elongated slot 33", and a threaded bolt 34 extends through the slot 33" into threaded engagement with the carrier plate 32. Thus, the bolt 34 may be tightened for fixing the angle member 33 to the carrier plate 32, and by loosening the bolt 34 it is possible to longitudinally shift the angle member 33 with respect to the plate 32, thus shifting the slot 3 3' with respect to the shank of the bolt 34, and thereafter the bolt 34 may be tightened, so that in this way it is possible to adjust the relationship between the contacts 35 and 36 of the interrupter means of FIG. 3, these contacts '35 and 36 respectively corresponding to the contacts 16 and 14 of FIG. 1. In order to shift the angle member 33 after the bolt 34- is loosened, for the purpose of adjusting the distance between the interrupter contacts 35 and 36, the support plate 32 is provided with a pair of projections 37 at its upper side, and the tip of a screwdriver is adapted to be placed between these projections in engagement with the rivet 38 on one side or the other side thereof so as to shift the holding member 33 in one direction or the other for adjusting the distance between the contacts 35 and 36 when these contacts are open. In order to guarantee that the angle member 33 moves longitudinally of the leaf spring 30 the angle member 33' is provided at its underside with a downwardly directed projection 33" which is located in an elongated notch 32' formed in the support plate 32, so that the pin 33" and the notch 32' cooperate to guide the angle member 3 3 for movement in a direction parallel to the spring 30.

With both of the above-described embodiments ott the invention, it is necessary, when the lever 27' turns, to overcome only an extremely small amount of friction, and the masses which are moved during turning of the lever 27' are relatively small. Moreover, it will be seen that a relatively large range of adjustment is provided for the components of the structure of the invention.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of distributors diifering from the types described above.

While the invention has been illustrated and described as embodied in interrupter assemblies of distributors, it is not intended to be limited to the details shown, since v 6 various modifications and structural changes may be made without departing in any Way from the spirit of the present invention. a

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a distributor for an internal combustion engine, in combination, a rotary cam turnable about its own axis; a stationary support plate located in a plane normal to said axis adjacent to said cam; interrupter means located next to said plate and including a stationary contact, a movable contact, and a cam follower portion located in the path of turning of said cam to be engaged thereby for moving said movable contact toward and away from said stationary contact; and a pair of link means respectively located on opposite sides of said cam, each link means being connected at one end portion to said interrupter means and at another portion to said plate, and said pair of link means supporting said interrupter means for movement with respect .to said plate in a plane parallel to said plate along a path which moves said cam tfollower portion, at least within a given range of adjustment of said interrupter means, along a circle whose center is in said axis.

2. In a distributor for an internal combustion engine, in combination, a rotary cam turnable about its own axis; a stationary support plate located adjacent said cam in a plane normal to said axis; interrupter means located next to said plate and including a stationary contact, a movable contact, and a cam follower portion located in the path of turning of said cam to be engaged thereby for moving said movable con-tact away from and back toward said stationary contact; and a pair :of Links respectively located on opposite sides of said cam, each having one end pivotally connected to said interrupter means, and each being also pivotally connected to said plate at a portion spaced from the pivotal connection to said interrupter means, said pair of links supponting said interrupter means for movement with respect to said plate in a plane parallel thereto along a path which moves said cam follower portion, within a given range of adjustment, along part of a circle whose center is in said axis.

3. In a distributor for an internal combustion engine, in combination, a rotary cam turnable about its own axis; a' stationary support plate located adjacent said cam in a plane normal to said axis; interrupter means located next to said plate and including a stationary contact, a movable contact, and a cam follower portion located in a path of movement of said cam to be engaged thereby for moving said movable contact with respectto said stationary contact; a first link means located on one side of said cam and having opposed end portions respectively connected with said interrupter means and with said support plate; second link means located on the other side of said cam, pivotally connected at one end to said interrupter means, and haw'ng a portion spaced fnom said one end and pivotally connected to said support plate, said first and second link means supporting said interrupter means for movement with respect to said plate in a plane parallel thereto along a path which moves said cam follower portion, at least within a given range of adjustment, along a circle whose center is in said axis; and an extension fixed to and extending from said second link means in a direction away from the connection thereof to said interrupter means, said extension forming an adjusting means for adjusting said interrupter means at least within said range.

4. In a distributor foran internal combustion engine,.

I contact, and a cam follower portion located in the path of movement of said cam to be actuated thereby for moving said movable contact with respect to said stationary contacnan elongated leaf spring located on one side of said cam and connected at one end to said plate and at its opposite end to said interrupter means; and a link located on the other side of said cam, pivotally connected at one 'end'to said interrupter means, and pivotally connected at a portion spaced from said one end to said plate, said link and leaf spring supporting said interrupter means for adjustable movement with respect to said plate along a path'which moves said cam follower portion, at least within a given range of adjustment, along a circle whose center is in said axis.

5. In a distributor for an internal combustion engine, in combination, a rotary cam turnable about its own axis; a stationary support plate located adjacent said cam in a plane normal to said axis; elongated interrupter means located next to said plate and extending across said cam, said interrupter means including a stationary contact, a movable contact, and a cam follower portion located in the path of movement of said cam' to be actuated thereby for moving said movable contact with respect to said stationary contact; and a pair of link means respectively located on opposite sides of said cam and each connected to said interrupter means and at a location spaced from said connection to said interrupter means to said plate,

the distance between the connection to said interrupter means and the connection to said plate of one link means being substantially equal vto the distance between the connection to said interrupter means and the connection to I 3 for moving said movable contact with respect to said sta tionary contact, said cam follower portion including a convex face engaged by said cam and forming part of a cylinder whose axis is parallel to and spaced from the axis of said cam; and a pair of link means respectively located on opposite sides of said cam and each connected to said plate and to said interrupter means, the distance between the connection of one link means to said interrupter means and to said plate being substantially equal to the distance between said axis and the distance between the connection of the other link means to said interrupter means and to said plate, said pair of link means supporting said interrupter means for movement 7 with respect to said plate along a path which moves said cam follower portion, at least within a given range of adjustment, along a circle whose center is in said axis of said cam.

said plate of the other of said link means, and said pair. t

of link means supporting said interrupter means for movement with respect to said plate in a plane parallel thereto along a path which moves said cam follower portion, at

least-within a given range of adjustment, :along a circle whose center is in said axis.

6. In a distributor for an internal combustion engine,

in combination, a rotary cam turnable about its own axis;

a stationary support plate located adjacent said cam in a plane normal to said axis; elongated interrupter means located next to said plate and extending transversely across said cam, said interrupter means having a stationary contact, a movable contact, and a cam follower portion located in the path of movement of said cam to be actuated thereby for moving said movable contact with respect to said stationary contact; firstlink means located on one side of said cam and having one end connected to said interrupter means and an opposite end connected to said plate; second link means located on the other side of said cam, having one end connected to said interrupter means, and having a portion spaced from said one end connected to said plate, said first and second link means supporting said interrupter means for movement in a plane parallel to said plate along a path which moves said cam follower portion, at least within a given range of adjustment, along a circle whose center is in said axis; an

elongated adjusting lever fixed to and extending from said second link means; and adjustable connecting means cooperating with said opposite end of said'first link means for adjusting the location of said opposite end of said first link means with respect to said plate.

7. In a distributor for an internal combustion engine, in combination, a rotary cam turnable about its own axis; astationary support plate located adjacent said cam in a plane normal to said axis; elongated interrupter means extending across saidcam and located adjacent said plate, said interrupter means including a stationary contact, a movable contact, and a cam follower portion locatedin the path of movement of said cam to be actuated thereby 8. In a distributor for an internal combustion engine, in combination, a rotary cam turnable about its own axis; a stationary plate located adjacent said cam in a plane normal to said axis; elongated'interrupter means located next to said plate and extending across said cam, said interrupter means including a stationary contact, a movable contact, and a cam follower portion located in the path of movement of said cam to be actuated thereby for moving said movable contact 'with respect to said stationary contact; and a pairtof link means respectively located on opposite sides of said cam, each connected to said plate and to said interrupter means, and said pair of link means forming withsaid interrupter means a parallogram linkage guiding said interrupter means for movement with respect to said plate along a path which moves said cam follower portion, at least within a given range of adjustment, alonga circletwhose center is in said axis.

9. In a distributor for an internal combustion, in combination, a rotary cam turnable about its own axis; a stationary support plate located adjacent said cam in a plane normal to said axis; an elongated two-armed lever pivotally connected intermediate its ends to said plate for turning movement with respect thereto about an axis parallel to said cam axis, said two-armed lever having one arm which forms an'adjusting means and is adapted to be moved in response to changes in the vacuum in the intake manifold of the internal combustion engine, said lever having a second arm overlying said plate and forminga first linkage means; pivot means carried by a said second arm to its end portion distant from the connection of said lever to said plate; elongated interrupter means pivotally connected at one end portion by said pivot means to said lever, said interrupter means including a stationary contact, a movable contact, an elongated lever carrying said movable contact and also pivotally supported by said pivot means, and a' camfollower portion carried by said elongated lever of said interrupter means located in the path of movement of said cam to be actuated thereby for moving said movable contact with respect to said stationary contact; and second linkage means located on the side of said cam opposite from said lever and connected atone end to said interrupter means and at its opposite end to said plate, said second linkage means cooperating with said first linkage means to guide said interrupter means for movement with respect to said plate along a path which moves said cam follower portion along a circle whose center is in said axis'of said cam, at least within a given range of adjustable movement of said first arm of said two-armed lever. t

a 10. In a distributor for, an internal combustion, in combination, a rotary cam turnable about its own axis; a stationary support plate located adjacent saidcam in a plane normal to said axis; an elongated two-armed lever pivotally connectedvintermediate its ends to said plate t 9 to be moved in response to changes in the vacuum in the intake manifold of the internal combustion engine, said lever having a second arm overlying said plate and forming a first linkage means; pivot means carried by said second arm at its end portion distant from the connection of said lever to said plate; elongated interrupter means pivotally connected at one end portion by said pivot means to said lever, said interrupter means including a stationary contact, a movable contact, an elongated lever carrying said movable contact and also pivotally supported by said pivot means, and a cam follower portion carried by said elongated lever of said interrupter means located in the path of movement of said cam to be actuated thereby for moving said movable contact with respect to said stationary contact; second linkage means located on the side of said cam opposite from said lever and connected at one end to said interrupter means and at its opposite end to said plate, said second linkage means cooperating with said first linkage means to guide said interrupter means for movement with respect to said plate along a path which moves said cam follower portion along a circle whose center is in said axis of said cam, at least within a given range of adjustable movement of said first arm of said two-armed lever; and adjustable connecting means connecting said second linkage to said plate at the end of said second linkage distant from said interrupter means for movement longitudinally of said second linkage means so that the location of the connection of said second linkage means to said plate can be adjusted for the purpose of regulating the cooperation between said movable and stationary contacts.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A DISTRIBUTOR FOR AN INTERNAL COMBUSTION ENGINE, IN COMBINATION, A ROTARY CAM TURNABLE ABOUT ITS OWN AXIS; A STATIONARY SUPPORT PLATE LOCATED IN A PLANE NORMAL TO SAID AXIS ADJACENT TO SAID CAM; INTERRUPTER MEANS LOCATED NEXT TO SAID PLATE AND INCLUDING A STATIONARY CONTACT, A MOVABLE CONTACT, AND A CAM FOLLOWER PORTION LOCATED IN THE PATH OF TURNING OF SAID CAM TO BE ENGAGED THEREBY FOR MOVING SAID MOVABLE CONTACT TOWARD AND AWAY FROM SAID STATIONARY CONTACT; AND A PAIR OF LINK MEANS RESPECTIVELY LOCATED ON OPPOSITE SIDES OF SAID CAM, EACH LINK MEANS BEING CONNECTED AT ONE END PORTION TO SAID INTERRUPTER MEANS AND AT ANOTHER PORTION TO SAID PLATE, AND SAID PAIR OF LINK MEANS SUPPORTING SAID INTERRUPTER MEANS FOR MOVEMENT WITH RESPECT TO SAID PLATE IN A PLANE PARALLEL TO SAID PLATE ALONG A PATH WHICH MOVES SAID CAM FOLLOWER PORTION, AT LEAST WITHIN A GIVEN RANGE OF ADJUSTMENT OF SAID INTERRUPTER MEANS, ALONG A CIRCLE WHOSE CENTER IS IN SAID AXIS. 